Beautiful graphics at the link. Why is it possible for the fastest person to be faster than the fastest person a century ago? I think that each man trained with the goal of winning in mind, and each knew how fast he needed to be to win. If Archie Hahn, the "Milwaukee Meteor," could win the 100-meter in 11 seconds, what could motivate him to shave his time down to 10 seconds?

As always the improvement is due to advances in the knowledge. The knowledge of diet, technique, training, and psychology, and also I think the level of dedication to it. Modern athletes make a career out of their sport, with everything else in life being put second, because great financial benefit can accrue, and that can justify total concentration to the it. This also expands the pool of participants. The potential fastest human 100 years ago, might very well have stayed on the farm, or in the factory, never to be discovered.

If you take Bolt back in time and train him with the knowledge and sports culture of the day, he would not likely be the fastest.

Also just logically the fastest are going to be more recent, because beating older records is the goal, and a way is always found to get to the goal.

Among other effects, statistics is a simple answer. There are a lot more people competing today than 100 years ago. Remember, the winner is at the far right edge of the bell curve, and the bell curve gets small fast as you move toward the extremes. 97.7% of people are less than two standard deviations to the right, 99.986% within three, and the number outside goes down fast. If there were ten million potential sprinters a century ago, that means that that ten-millionth fastest person is likely to be a certain number of standard deviations out from the mean (a little over 5). If there are (as there are today), more like 5 billion potential sprinters, you are likely to find some people a little more over to the right (almost 6 and a half standard deviations, actually).

The same holds true for baseball skills, now that Japan is included, and Nobel Prizes.

And don't forget, the olympic gold medalist is not necessarily the best in the world, but merely the best from a narrow privileged group that had the opportunity, support, and luck to have their talents spotted and nurtured early.

It's a pool that is easily expanded. You may have had gold medal potential, but never tried that particular sport. (One of my favorite movie lines: "I'm not an idiot, I'm an idiot savant! I just haven't found my savant yet.")

All those improvements... and they can only go 1 second faster. Seems like decline!

More like slightly more than three seconds. That's about a 25% improvement over the shortest race available. In the Marathon, times have improved about as much: from about 179m to about 130m, about 27%.

Something that impressed me from this chart: Jesse Owens was at 10.3 seconds in 1936. It took another 36 years for someone to win a gold with a faster time; and he's only 0.7 sec behind Bolt. (Yeah, I know, 0.7 sec is an eternity in this race; but this was nearly a century ago.)

How fast would Owens have been, had he had modern training, equipment, track, diet, etc? And as Alhouse pointed out -- if Owens had been pushed to go faster than 10.3 sec?

Numbers, nutrition, equipment, training and a goal to simply beat the last guy by any time, however small.

(The track does make a difference which raises the question of whether artificial track surfaces should be allowed. I'm genuinely curious how fast would Bolt run on a cinder track comparable to that Jesse Owens used in Berlin, 1936.)

Here's an experiment. Construct a track the same as that used in the 1936 Olympics and dress Bolt and the competitors in gear the same as Owens and see what their times are. I wonder if they'd break 10 seconds.

Speed in sprinting involves two factors -- leg speed and length of stride.

Improved times are due probably not so much to the shoes. A sprinter's shoe, at least when I was running years ago, is very thin, essentially a sock with spikes on it. Perhaps the shoes have gotten bigger and springier since then, but that would surprise me since it would make them heavier. That said, amputees using special prosthetics can be made to be a lot faster because of the spring effect.

Track conditions are probably the biggest factor. Improved tracks can probably add an inch or two per stride, which can translate into a foot or two over 100 yards, or a few tenths of a second.

Weight training and improved nutrition are probably the other factors to allow for the legs to move more quickly and to extend the stride a little bit more.

Finally, special hi-tech uniforms can reduce wind drag a little bit, but reducing it a little bit is all you need to shave off a few fractions of a second.

People a couple of decades ago were short -- or at least one person was short.

When I first started running track, I was fasted guy out there.

Then, as we got older and grew, everyone else's legs got longer than mine did. Consequently, their length-of-stride increased and eventually overcame their slower leg speed, such that I could no longer compete with them.

A product of separate competitions, each of which has heated up. Competition among venues to host record setting performances. Competition among equipment vendors to equip the best performers. Competition among trainers. Finally competition among runners. Each competitor was focused on beating his current peers. And the rewards of success have gotten richer over the years. (Olympics used to be for amateurs.)

Understanding of physiology has increased greatly over the years. The "Milwaukee Meteor" probably didn't have coaches videotaping and analyzing his every move and stride and breaking it all down to the tenth of a second (or less).

Great Britain’s Greg Rutherford delighted the crowd at the Olympic Stadium by claiming victory, but his winning distance ((( was the worst performance by a Games gold medalist in the event for 40 years. )))

Ever since Randy Williams of the United States took gold in Munich in 1972, every champion has jumped at least 8.34 meters, with a high point of Carl Lewis’ winning leap in Seoul in 1988 of 8.72.

As mentioned by some already: track technology and sneaker/uniform technology. Also, training has become a science. Not only have actual techniques been revolutionized like intervals and weight training, but they have designed the training programs to achieve a peak performance at a certain time. A months-long program can have a runner at his best possible time when he needs it, which leads to body preservation. Bolt likely does not run this fast year-round, and his times likely have improved a little each race up until now.

Also, don't leave out the psychological factor either. When Roger Bannister ran 3:59.4, the WR for the mile had stood for 5 years at 4:01.4. Within 5 years after Bannister, 3 other men had broken it and shaved nearly 5 more seconds off. People had always thought that 4:00 was a barrier that the human body and heart simply could not endure.

That being said, there has to be a point where the fastest will stand since the logical conclusion "ever record can be broken" would eventually lead to a 0.001 sec 100m

Also the technology that records races is much better than it was 100 yrs ago. I wonder how exact times would be using 100 y/o tech. That is one reason I am somewhat skeptical of temperatures of 100 years ago vs today. Much more accurate tech.

Don't discount genetics. Watching Secretariat destroy competition in his races makes me think that sometime, somewhere, that freak athlete is going to turn up, and crush these records. Probably not in the 100 meters, there's just not enought time in the race...

I thought this sounded cynical at first, but even if we were to give the benefit of the doubt to any athlete suspected of juicing, you might say that the effect of any "performance enhancing drug" (if such a thing existed) that was used in past eras would fall well below the technology that goes into the supplements and non-banned substances that are commonplace these days.

On a related note, the question of what should or should not be labeled a "performance-enhancing drug" has always bugged me.

" Why is it possible for the fastest person to be faster than the fastest person a century ago? I think that each man trained with the goal of winning in mind, and each knew how fast he needed to be to win."

Usain Bolt is 6'5", 210 lbs.Archie Hahn was 5'6" 140 lbs.

Motivation has nowhere near the importance to which you ascribe it. All the "want to" in the world could not compensate for the fact that Archie needed 49 strides to cover 100 meters, while Bolt needs just 41.